According to the meaning of the terms used herein, dialysis devices are in particular devices for the extracorporeal blood treatment, which for example can be configured for haemodialysis and/or ultrafiltration.
During haemodialysis, the blood of a patient in a dialysis device is led in an extracorporeal blood cycle through a blood chamber of a dialyzer. The blood chamber is separated by a semipermeable membrane from the dialysis chamber of the dialyser. The dialysis chamber is perfused by a dialysate. The dialysate contains blood electrolytes in a concentration that corresponds to the concentration in the blood of a healthy individual. During the treatment, the blood and the dialysate are led past opposite sides of the semipermeable membrane in general in a counterflow with a predetermined flow rate. The substances, which should be excreted by urine diffuse through the membrane from the blood chamber into the dialysis chamber, while at the same time electrolytes that are present in the blood and in the dialysate diffuse from the chamber of higher concentration to the chamber of lower concentration.
Additionally the blood can be dehydrated by building up a pressure gradient on the semipermeable membrane of the dialyser, and as a consequence water is pressed out of the blood to the side of the dialysate chamber. This process is called ultarfiltration.
The effectiveness of the dialyser in the dialysis device and, thus, in the blood treatment inter alia also depends on the size of the dialysate flow, i.e. the flow rate of the dialysate. A high dialysate flow can increase the effectiveness of the blood treatment up to an upper limit, however, also leads to an increase of the consumption of dialysate and energy.
Accordingly, it is desirable and thus an object of the invention to determine the amount of dialysate flow in a dialysate device such that the effectiveness of the blood treatment is as high as possible and at the same time the consumption of dialysate and energy is kept in an acceptable range. Thereby it is further desirable that such a definition of the amount of dialysate flow can be carried out independently of the knowledge of the used dialyser type, the blood flow or specific patient parameters, as for example the presence of a recirculation.